Placing a keypad or the like on an exterior surface of a vehicle can be a good way to receive user input to allow access to the vehicle. Vehicle windows cover a significant portion of a vehicle's exterior surface, and typically are located at a height convenient for a user to access. However, mechanisms for accepting input on a window are lacking for a number of reasons. First, there are specific areas windows must be kept clear during operation of a vehicle per government regulations, meaning that a conveniently placed physical touchpad, which would require some physical structure to be physically attached to a window, would violate clear area requirements. Further, due to vehicle windows (at least side windows) being moveable, there are durability and cost challenges with interfacing electronics to a window-mounted touchpad. Additionally, the fact that vehicle windows are curved presents further cost challenges to implementing a non-physical, i.e., virtual, input mechanism on a vehicle window.